Stabilized mineral oil



Aug. 27, 1935.

B. H. SHOEMAKER 2,612,918

STABILIZED MINERAL OIL Filed Nov. 5, 1952 s Sheets-Sheet 2 Q U "D o .50.100 J60 .Tz'r/ze z'nfioara INVENTOR Fig. 2 flermr'dfijlzoemakerATTORNEY Aug. 27, 1935.

True Color B. H. SHOEMAKER STABILIZED MINERAL OIL Filed Nov. 3, 1932 3Sheets-Sheet 3 2o 40 60 so .200 .120 .240 160 J'Z'me iniocma INVENTORfier'izard flzoemker ATTORNEY Patented Aug. 27, 1935 STILIZED RAL OILBernard Harvey Shoemaker, Hammond, Ind., assignor to Standard OilCompany, Chicago, BL, a corporation of Indiana Application November 3,1932, Serial No. 640,968

14 Glaims.

This invention relates to the stabilization of mineral oils and itpertains more particularly to a process and composition for preventingsludge and color formation in lubricating oils when used underconditions conducive to deterioration.

Mineral oils, and particularly lubricating oils, when used in internalcombustion engines or under conditions where the oils come in contactwith hot surfaces, deteriorate and form sludge,

deteriorate in color, form varnish-like products that deposit on thesurfaces being lubricated and the viscosity of the oil increases withuse. This deterioration of mineral oils is particularly noticeable withoils used to lubricate internal ,combustion engines used in motorvehicles and. aeroplanes. The sludge formed collects on the piston ringsand causes them to stick. Also, sludge collects in the oil pumps and oillines arn'i'greatly retards the flow of oil and in some cases plugs upthe oil lines and small passages;

The object of my invention is to provide a method for stabilizingmineral oils, and particularly lubricating oils, against deterioration.j

Another object is to provide a method forinhibiting the sludge formationof mineral oils by adding to the-oil an inhibiting catalyst.

Another object is to prevent the increase in viscosity of the oil uponcontinued use.

Another object is to provide a method for preventing color deteriorationof the oils.

A further object is to provide a process for preventing the formation ofvamish-like products in lubricating oils and the staining of the partsto be lubricated.

In internal combustion engines it is very important that the lubricatingoils be stable against 4 cessive oil consumption and loss ofcompression.

Thecurve in Figure 1 illustrates the tendency of a heavy Mid-Continentlubricating oil to form sludge with increase in temperature. It will beobserved that at 320 F. it required about 54 hours for 10 grams of oilto form 10 mg. of sludge, whereas at 360 F. it required only 19 hours toform 10 mg. of sludge. It is very important to note that a relativelysmall increase in temperature will greatly increase the rate of sludgeformation. The sludge stability of the oil with reference totemperature, shown in Figure 1, was determined by heating a quantity ofoil to the desired temperature and bubbling air through the sample atthe rate of 10 liters per hour. At intervals, 10 gram samples werewithdrawn and tested for sludge by the precipitation method described inAmerican Society of Testing Materials Proceedings, volume 24, page 967.

Another undesirable characteristic of lubrieating oils is their changeof viscosity upon use. The curve shown in Figure 2 illustrates thisproperty of mineral oils. It will be observed that the Saybolt viscosityincreases greatly upon use. The results expressed by the curve in Figure2 were obtained by maintaining a Pennsylvania oil at 340 F. and bubblingpreheated air through the oil at the rate of to liters per hour. It isapparent that when-mineralolls are used at ele vated temperatures ininternal combustion engines, the viscosity increases upon continued use,and the oil will become so viscous that a heavy load is put upon theengine, especially when starting. This is particularly noticeable incold weather.

Another common and undesirable property of mineral oils, andparticularly those lubricating oils used in contact with hot surfaces,such as in internal combustion engines, is the development of color. Thecurve in Figure 3 shows the rate of color formation when a heavyMid-Continent lubricating oil is heated to 340 F. while air is bubbledinto the oil at the rate of 10 liters per hour.

I have found that mineral oils, and particularly lubricating oils, canbe stabilized against deterioration as illustrated by sludge formation,increase in viscosity upon use, staining of the surfaces to belubricated and color formation, by adding to the oil a small quantity ofan alkaline metal amide such as an alkali metal or alkaline earth metalamide. The amides suitable for my invention have the following generalformula:

wherein X represents an alkaline monovalent metal such as the alkalimetals, X1 represents a divalent alkaline metal such as the alkalineearth metals, and R and R1 may represent hydrogen atoms, alkyl, aryl,and/ or aralkyl groups. Examples of these amides are the alkyl anddialkyl alkali metal amines such as diethyl sodamide, dipropylsodamides, dimethyl sodamides, dibutyl sodamides, diamyl sodamides,dihexyl sodamides hexyl sodamides, amyl sodamides, butyl sodamides,propyl sodamides, ethyl propyl sodamides, ethyl butyl sodamides, ethylamyl sodamides, propyl butyl sodamides, isopropyl butyl sodamides,methyl ethyl sodamide, methyl propyl sodamides, methyl butyl sodamides,di-isopropyl sodamide, and the like; aryl alkali metal amides such asphenyl sodamide, naphthyl sodamide,

phenyl methyl sodamide, phenyl ethyl sodamide,

phenyl butyl sodamides, diphenyl sodamide, naphthyl methyl sodamides,benzyl sodamide, dibenzyl sodamide, also the sodamides (Na-N compounds)of other aromatic amines such as the toluidines, chloroanilines,aminophenols, benzidine, and the like may be used. It should beunderstood that instead of using the sodium derivatives, I may use otheralkali metal or alkaline earth metal derivatives such as potassium,lithium, calcium, magnesium, barium and the like.

The stabilized oils are prepared by dissolving and/or dispersing a smallamount of a metal amide therein. The preferred amounts range from 0.1 to0.001%, the amount varying with specific materials, however, largeramounts up to 1% may be used, if desired.

The following" table illustrates the results obtained when a heavyMid-Continent lubricating oil is stabilized with an alkali metal amide.These tests were obtained by heating a quantity of oil at 340 F. andbubbling air into the oil at the rate of 10 liters per hour. Atintervals, a 10 gram sample of oil is withdrawn and tested withdrawn andmay be recycled to the colloidal mill and reused.

The following table shows that the alkaline amides such as the alkalimetal amides and the alkaline earth metal amides are also particularlyeffective for inhibiting color formation. This table shows the colorstabilizing effect of sodamide (NaNHz) when added to a heavy lubricatingoil.

It is apparent that the amides are particularly effective for inhibitingcolor formation. Instead ofusing sodamide I may use the amides of otheralkaline metals such as calcium, barium, magnesium, potassium, lithium,aluminum and other metals of equal alkalinity.

Instead of using the amides stabilizing motor oils for use in internalcombustion engines or for stabilizing hydrocarbon oils at elevatedtemperatures, they may be used to stabilize hydrocarbon oils duringstorage.

The term stabilizing is used in my application in a generic sense toinclude the preserving of the oil against deterioration in any of theforegoing respects, such as sludge formation, color formation, increasein viscosity, and/or the formation of varnish-like products. The alkaliamides used in my invention do not appear to function as reducing agentsand their stabilizing action cannot be definitely explained by thetheory upon which for sludge. the action of antioxidants are explained.How- Table I Sludging time in True color hours to formafter- ExampleStabilizer Percent 10 mg. mg. 1 Control 29 44 1435 2000 2 Dibutylsodamide 0.3 37 63 740 3 Diethyl sodamide-.." 0.2 60 60 480 4 Sodamide(NaNHz). 0.5 Over 103 From the above table it is apparent that thealkali amides are very effective for inhibiting sludge formation. Forexample, it required 37 hours for 10 mg. of sludge to form when an oilwas stabilized with 0.3% of dibutyl sodamide, whereas it required only29 hours for the unstabilized oil to form 10 mg. of sludge. Also thetrue color of the stabilized oil was only 175 after 15 hours, whereasthe control had a color of 1435. The low molecular weight amides such asdiethylsodamide and sodamide are particularly effective for preservingthe oil. If larger amounts of the alkyl amides are used, greaterstability can be obtained. 7

Instead of adding the alkaliamides to the oil, these compounds may beprepared in situ by dispersing colloidal sodium in the oil and thenadding ammonia or a suitable alkyl or aromatic amine. Also the aminesmay be passed through a colloidal mill with the sodium and oil to bestabilized. After the amines and alkaline metal have had time to react,the excess sodium is ever, it is thought that the deterioration ofmineral oils is accompanied by the formation of interme-' diate acidicproducts, and the alkali derivatives of amines retard the formation ofthese intermediate acidic products and thereby stabilize the oil againstdeterioration.

While I have described my invention with reference to certain oils andcompounds, the scope of my invention is not limited thereby exceptinsofar as set forth in the claims.

I claim: a

1. The process for stabilizing hydrocarbon oils against deteriorationwhich comprises adding a small proportion of an oil soluble amide havingthe following general formula:

R X1: N

wherein X1 represents a divalent alkaline metal and R and R1 representalkyl, aryl or aralkyl groups.

R X N wherein X represents an alkali metal and R represents an alkylgroup or hydrogen atom and R1 represents an alkyl group.

4. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding a small proportion of an amidehaving the following general formula:

wherein X represents an alkali metal, R represents a hydrogen atom andR1 represents an alkyl group.

5. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding a small proportion of an amidehaving the following general formula:

R X N wherein X represents an alkali metal, R represents a hydrogen atomand R1 represents an aryl group.

6. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding a small proportion of an amidehaving the following general formula:

R XN wherein X represents an alkali metal, R represents a hydrogen atomand R1 represents an aralkyl group.

7. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding a small proportion of an amidehaving the following general formula:

R X -N wherein X represents an alkali metal, R represents an alkyl groupand R1 represents an aralkyl group.

8. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding thereto a small proportion of adialkyl alkali metal amide.

9. The process for stabilizing hydrocarbon mineral oils againstdeterioration which comprises adding thereto a small proportion of anamide selected from the group consisting of dibutyl sodamide, diethylsodamide, dipropyl sodamide, ethyl butyl sodamide, and amyl sodamide.

10. A hydrocarbon lubricating oil containing a small proportion of anamide having the general formula:

wherein X represents an alkali metal, R and R1 may represent hydrogenatoms, alkyl, aryl or aralkyl groups.

11. A hydrocarbon lubricating oil containing a small proportion of anamide having the general formula:

wherein X represents an alkali metal, R represents a hydrogen atom or analkyl group, and R1 represents an alkyl group.

12. A hydrocarbon lubricating oil containing a small proportion of anamide having the general formula:

R XN wherein X represents an alkali metal, R represents a hydrogen atomand R1 represents an aryl group.

13. A sludge resistant mineral oil comprising a viscous hydrocarbon oiland from 0.1 to 0.5% of a dialkyl alkali metal amide.

14. A sludge resistant mineral oil comprising a viscous hydrocarbon oiland from 0.1 to 0.5% of an amide selected from the group consisting ofdibutyl sodamide, diethyl sodamide, and ethyl propyl sodamide.

BERNARD HARVEY SHOE-MAKER.

